The present invention relates to a method of forming light permeable panels so that a viewer on one side of the panel can observe two different or discrete images on the panel dependent upon the intensity of light incident on opposite sides of the panel and particularly to a perforated panel having retroreflective material.
According to my invention as disclosed in my U.S. Pat. No. 5,679,435, there is provided a vision control panel made up of an retroreflective opaque sheet material with a dark color on the reverse side and an image formed on one surface of the opaque sheet. The opaque sheet and retroreflective image have a plurality of perforations formed by a laser, the perforations being spaced thereover such that when the light level on the image side of the panel is slightly less than, equal to, or greater than that on the other side, an observer on the image side sees only the image while an observer on the other side sees through the panel without seeing the image. By laser perforating, the entire image or design, one avoids blocking vision through the design from the side opposite the image side. Moreover, in fabricating the panel there is no need to align inks forming the design as would be the case in prior methods using ink dots on a light permeable, transparent, non opaque sheet.
The retroreflective material comprises an opaque sheet of material, preferably vinyl, using glass beads or metallized particles formed between various substrates of adhesives, colored sheet materials and other laminates. These retroreflective sheet materials may then be over-printed with translucent light permeable inks which allow light to pass therethrough allowing for light reflection of the colored image and design of 100, 200, 300 candle power and more for improved viewing properties under varying light conditions.
Preferably the image is formed by at least two different colors in the form of a design. A transparent sheet containing a U.V. chemical resistor may be used to cover the image on either side of the sheet material to prevent dirt or rain drops from entering the perforations and to protect the pigments of the colors from rapid sun fading. The placement of the transparent sheet on one side as opposed to the other side depends on whether the sheet material is to be attached to the inside or outside of the window or glass. The assembly methods used for attachment of the transparent protective sheet vary depending on visibility requirements. In one method of making a vision control panel, there is no glue or adhesive coating the transparent sheet material therefor there is no possibility for the glue to yellow in the transparent regions of the perforated panel. In another method of making a vision control panel, the transparent protective sheet material has a clear adhesive coating which eliminates the requirement of a transfer adhesive first applied to the retroreflective sheet material prior to perforation.
In another aspect of the invention of my prior patent, there is provided a method of forming a vision control panel which includes forming a combination of pre selected retroreflective light reflecting films overlaid with translucent ink colors or films and an underlying dark colored opaque light absorbing color or film and then laser perforating the combination to form a matrix of spaced apart small apertures over the combination of such a density that a viewer of the opaque dark colored side can see through the panel but a viewer on the other side sees only the retroreflective light reflecting colors and image thereon. Preferably the diameter of each of the apertures is small enough so that the individual holes are not easily distinguishable by a viewer. The individual holes may be formed by a plurality of spaced apart dies or preferably by laser perforation which will remove the small plugs from the material without gumming up the dies normally caused by adhesives contained within the assembled sheet material.
Advantageously, the retroreflective light reflecting film may have a white color overlaid on a dark color. The white side of the retroreflective film is then coated with light reflecting particles such as glass beads, metallizing or other light reflecting particles held in place by a clear top coating. Additional translucent light permeable colors may then be overlaid over the retroreflective light reflecting white film. The translucent light permeable colors may be applied over the retroreflective sheet material before or after perforating. The sheet material may be vinyl containing retroreflective particles.
According to the present invention, a retroreflective vision control panel is provided having two discrete images observable from one side of the panel, i.e., the retroreflective side of the sheet material, depending upon the relative intensities of light incident on opposite sides of the panel. To accomplish this, sheet material having retroreflective material on one side and an opaque surface on the opposite side with translucent image-forming material, such as inks, overlying the retroreflective material and defining a first image are formed. An array of laser-formed perforations are provided through that sheet material, including the retroreflective and light-permeable materials. Additionally, and in accordance with the present invention, a non-perforated light-permeable material is provided on the side of the sheet material opposite the retroreflective material and lies at least in part in registration with the perforations through the sheet material. Light-permeable material, for example, translucent inks, are employed to form a second image on the non-perforated light-permeable material. In this manner, depending upon the relative intensities of light incident on opposite sides of the panel, an observer on one side of the panel (the perforated side) sees either one or the other of the first and second images on the panel.
As a representative example of the environment in which the control panel of the present invention may be used, the panel may be adhered to the inside of a display window of a store by using suitable clear adhesives with the retroreflective material preferably on the side of the sheet material facing the window. If the inside of the display window is dark or dimly lit, light incident on the outside of the window (the front side of the panel) and particularly on the translucent inks and retroreflective material, enables the first image formed on the retroreflective material to be seen from outside the display window, the image being one of very substantial intensity. Conversely, if the inside of the display window is brightly lit, and the outside of the display window is dark or only ambient non-intense light is applied, the light incident on the back side of the vision control panel enables the second image to be observed from outside the display window through the perforations of the sheet material. With very little or very dim light on the outside of the display window, the first image is not visible to an observer outside of the display window. The present vision control panel is particularly useful as a stand-alone panel having its own back light, for example, as confined in a light box wherein back light can be selectively applied. When turned off, light incident on the retroreflective or front side of the panel causes the first image to be observed from the front side of the panel. When the back light is turned on, to an intensity brighter than light incident on the retroreflective or front side of the panel, the backlit image dominates and is observed from the retroreflective side of the material.
Accordingly, it is a primary object of the present invention to provide a novel and improved vision control panel in which two images are selectively observable from one side of the panel dependent upon the intensity of light incident on opposite sides of the panels.
In a preferred embodiment according to the present invention, there is provided a retroreflective vision control panel for forming discrete images observable from one side of the panel, comprising sheet material having retroreflective material on one side of the sheet material and having an opaque surface on an opposite side thereof, light-permeable material comprising a translucent image-forming material overlying the retroreflective material and defining a first image on one side of the sheet material, an array of laser-formed perforations through the sheet material including through the retroreflective and light-permeable materials, the perforations forming 10-68% of open area through the sheet material and the retroreflective and light-permeable materials, such that an observer on one side of the sheet material sees the first image on the retroreflective material formed by the translucent material dependent on the relative intensity of light incident on opposite sides of the panel, a non-perforated light-permeable material on a side of the sheet material opposite the retroreflective material and at least in part in registration with the perforations through the sheet material, a light-permeable material comprising a translucent image-forming material on the non-perforated light-permeable material and defining a second image such that an observer on one side of the sheet material sees the second image through the perforations dependent on the relative intensity of the light incident on opposite sides of the panel, whereby the relative intensities of light incident on opposite sides of the panel determine the visibility of one or the other of the first and second images from one side of the panel.
In a further preferred embodiment according to the present invention, there is provided a method of forming a vision control panel for forming discrete images selectively observable from one side of the panel in accordance with the relative intensity of light incident on opposite sides of the panel, comprising the steps of laser-perforating a sheet material having a retroreflective surface on one side of the panel and an opaque surface on an opposite side of the sheet material to form an array of perforations through the sheet material, applying a light-permeable material in overlying relation to the retroreflective surface to define a first image on one side of the sheet material whereby the image on one side of the sheet material is observable from one panel side, applying a non-perforated light-permeable material on a side of the sheet material opposite the retroreflective material and forming a second image adjacent the opposite side of the sheet material and observable through the perforations through the sheet material from one panel side, thereby forming a vision control panel whereby the relative intensity of light incident on the opposite sides of the panel determines the visibility of one or the other of the first and second images from one panel side.